Silencer for a vehicle air conditioning system

ABSTRACT

A silencer for a vehicle air conditioning system is designed to reduce a noise and a vibration of a compressor transmitted into a vehicle room along coolant pipes. The silencer includes a silencer body tube and an external resonance tube. The silencer body tube is installed between the coolant pipes wherein a coolant gas flowing along the coolant pipes passes through the silencer body tube, the silencer body tube including one or more resonance holes formed on an outer circumferential surface of the silencer body tube. The external resonance tube is installed on the outer circumferential surface of the silencer body tube wherein a resonance chamber for absorbing a vibration and a noise of a coolant gas flowing through the silencer body tube is defined between the outer circumferential surface of the silencer body tube and the external resonance tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No.10-2013-0100485 dated Aug. 23, 2013, Korean Patent Application No.10-2013-0105961 dated Sep. 4, 2013, and Korean Patent Application No.10-2014-0001813 dated Jan. 7, 2014, each of which is hereby incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a silencer for a vehicle airconditioning system and, more particularly, to a silencer for a vehicleair conditioning system capable of efficiently reducing a vibration anda noise of a compressor without impairing the fluidity of a coolantwhile suppressing stagnation of a compressor lubricant.

BACKGROUND OF THE INVENTION

Noise is one major cause of reducing vehicle ride comfort. There aremany different kinds of noises generated in a motor vehicle, including anoise of an air conditioner. The noise of an air conditioner isgenerated in a process of compressing a coolant in a compressor. If thenoise is introduced into a vehicle room, vehicle ride comfort issignificantly reduced.

In particular, a vibration and a noise generated in a compressor aretransmitted into a vehicle room along a coolant and a coolant pipe. Dueto the vibration and the noise thus transmitted, a vehicle occupantresiding within a vehicle room receives a severe stress and feelsfatigue. Thus, the vibration and the noise reduce vehicle ride comfortand significantly hinder safe driving. Accordingly, the noise generatedfrom the compressor of the vehicle air conditioning system needs to bereduced in order to improve vehicle ride comfort and to assure safedriving.

As a method of reducing a noise generated in a compressor, there isavailable a technology in which a silencer is installed in a coolantpipe connected to the compressor.

As shown in FIG. 1, this technology makes use of a Helmholtz resonanceprinciple and has a structure in which a resonance tube 3 is installedwithin a coolant pipe 1. The resonance tube 3 includes a coolantintroduction portion 5, a neck portion 7 whose diameter graduallydecreases from the coolant introduction portion 5, and a coolantdischarge portion 9 whose diameter gradually increases from the neckportion 7. A resonance chamber 7 a is defined between the outercircumferential surface of the neck portion 7 and the innercircumferential surface of the coolant pipe 1.

In this resonance tube 3, during a process of introducing anddischarging a coolant gas having a high temperature and a high pressure,a vibration and a noise is absorbed into the resonance chamber 7 athrough a resonance hole 7 b formed in the neck portion 7. As a result,the vibration and the noise generated in the compressor are preventedfrom being transmitted into a vehicle room through the coolant and thecoolant pipe. This makes it possible to prevent deterioration of vehicleride comfort which may be caused by the vibration and the noisegenerated in the compressor.

In the conventional air conditioning system mentioned above, the coolantgas having a high temperature and a high pressure should pass throughthe resonance tube 3 having a small diameter. This leads to a sharpdecrease in the coolant fluidity, which in turn results in a decrease inthe vehicle room cooling performance.

Oil for lubricating the compressor is contained in the coolant gas. Asshown in FIG. 2, the oil passing through the neck portion 7 of theresonance tube 3 is introduced through the resonance hole 7 b and isstagnated in the resonance chamber 7 a as indicated by “A”. This reducesthe performance of the compressor and significantly reduces the noiseabsorption performance of the resonance chamber 7 a.

Particularly, oil shortage occurs in the compressor due to thestagnation of the oil in the resonance chamber 7 a. This may drasticallyreduce the compressor performance and may cause trouble in thecompressor.

The stagnation of the oil in the resonance chamber 7 a leads to adecrease in the effective volume of the resonance chamber 7 a and asharp reduction in the noise absorption performance of the resonancechamber 7 a. As a consequence, the efficiency of reducing the noise andthe vibration of the compressor is significantly reduced.

SUMMARY OF THE INVENTION

In view of the above-noted problems, it is an object of the presentinvention to provide a silencer for a vehicle air conditioning systemcapable of efficiently absorbing a vibration and a noise of a compressortransmitted through a coolant and a coolant pipe without impairing thecoolant fluidity.

Another object of the present invention is to provide a silencer for avehicle air conditioning system capable of efficiently reducing avibration and a noise of a compressor without impairing the vehicle roomcooling performance.

A further object of the present invention is to provide a silencer for avehicle air conditioning system capable of efficiently absorbing avibration and a noise of a compressor transmitted through a coolant anda coolant pipe while preventing stagnation of oil.

A still further object of the present invention is to provide a silencerfor a vehicle air conditioning system capable of suppressing a reductionin the compressor performance and a reduction in the vibration/noiseabsorption rate, which may be caused by stagnation of oil.

In order to achieve the above objects, the present invention provides asilencer for a vehicle air conditioning system designed to reduce anoise and a vibration of a compressor transmitted into a vehicle roomalong coolant pipes (30), including:

-   -   a silencer body tube installed between the coolant pipes such        that a coolant gas flowing along the coolant pipes passes        through the silencer body tube, the silencer body tube including        one or more resonance holes formed on an outer circumferential        surface of the silencer body tube; and    -   an external resonance tube installed on the outer        circumferential surface of the silencer body tube such that a        resonance chamber for absorbing a vibration and a noise of a        coolant gas flowing through the silencer body tube is defined        between the outer circumferential surface of the silencer body        tube and the external resonance tube,    -   the silencer body tube configured to restrain        compressor-lubricating oil introduced into the resonance chamber        through the resonance holes from being stagnated in the        resonance chamber.

In the silencer for a vehicle air conditioning system according to thepresent invention, the resonance chamber is formed outside the silencerbody tube. This makes it possible to efficiently absorb a vibration anda noise of a coolant gas without having to reduce the inner diameter ofthe silencer body tube.

Since the vibration and the noise of the coolant gas can be efficientlyabsorbed without having to reduce the inner diameter of the silencerbody tube, it is possible to efficiently absorb the vibration and thenoise of the coolant gas without impairing the fluidity of the coolantgas flowing through the coolant pipe.

Just as the vibration and the noise of the coolant gas can beefficiently absorbed without impairing the fluidity of the coolant gas,it is also possible to efficiently reduce the vibration and the noise ofthe compressor without impairing the vehicle room cooling performance.

According to the present invention, the oil introduced into theresonance chamber is allowed to flow down in the gravity direction andis discharged to the silencer body tube and the coolant pipe. It istherefore possible to prevent stagnation of oil in the resonancechamber.

Since the stagnation of oil in the resonance chamber can be prevented,it is possible to suppress a reduction in the compressor performance anda reduction in the vibration/noise absorption rate, which may be causedby the stagnation of oil in the resonance chamber.

The accurate assembling position of the external resonance tube ismarked on the silencer body tube in advance. The external resonance tubeis assembled on the basis of the mark. It is therefore possible torapidly and accurately assemble the external resonance tube in a correctposition.

Just as the external resonance tube can be rapidly and accuratelyassembled in a correct position, it is possible to perform theassembling work of the external resonance tube in an easy and rapidmanner and to precisely arrange the external resonance tube with respectto the resonance hole.

Since the assembling work of the external resonance tube can beperformed in an easy and rapid manner and since the external resonancetube can be accurately assembled in a correct position, it is possibleto enhance the productivity and to significantly improve the noiseabsorption performance of the silencer.

In one embodiment of the invention, a silencer for reducing noise andvibration transmitted through a coolant pipe conveying a coolant gas anda lubricating oil therethrough comprises a silencer body tube and anexternal resonance tube. The silencer body tube includes at least oneresonance hole formed in an outer circumferential surface thereof. Theexternal resonance tube is disposed around the outer circumferentialsurface of the silencer body tube, wherein a resonance chamber forabsorbing a vibration and a noise of the coolant gas flowing through thesilencer body tube is defined between the outer circumferential surfaceof the silencer body tube and the external resonance tube. The at leastone resonance hole provides fluid communication between the silencerbody tube and the resonance chamber and lubricating oil introduced intothe resonance chamber flows downward in a gravity direction and isdischarged into the silencer body tube through the at least oneresonance hole.

In another embodiment of the invention, a silencer body tube includes atleast one resonance hole formed in an outer circumferential surfacethereof, wherein the silencer body is disposed coaxially with and influid communication with the coolant pipe to cause the coolant gasflowing through the coolant pipe to flow through the silencer body tube.The silencer body tube has an inner diameter substantially equal to theinner diameter of the coolant pipe. An external resonance tube isdisposed around the outer circumferential surface of the silencer bodytube, wherein a resonance chamber for absorbing a vibration and a noiseof the coolant gas flowing through the silencer body tube is definedbetween the outer circumferential surface of the silencer body tube andthe external resonance tube and each of the at least one resonance holesprovides fluid communication between the silencer body tube and theresonance chamber. One of the resonance holes is formed in a gravitydirection lowermost portion of the silencer body tube surrounded by theresonance chamber and lubricating oil introduced into the resonancechamber flows downward in a gravity direction and is discharged into thesilencer body tube through the one resonance hole.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of preferred embodiments,given in conjunction with the accompanying drawings.

FIG. 1 is a sectional view showing a conventional silencer for a vehicleair conditioning system;

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

FIG. 3 is a sectional view showing a silencer for a vehicle airconditioning system according to a first embodiment of the presentinvention;

FIG. 4 is a sectional view showing a silencer for a vehicle airconditioning system according to a second embodiment of the presentinvention;

FIG. 5 is a sectional view showing a silencer for a vehicle airconditioning system according to a third embodiment of the presentinvention;

FIG. 6 is a sectional view showing a silencer for a vehicle airconditioning system according to a fourth embodiment of the presentinvention;

FIG. 7 is a sectional view taken along line VII-VII in FIG. 6;

FIG. 8 is a sectional view showing a modified position of one of theresonance holes of the silencer according to the fourth embodimentillustrated in FIG. 6;

FIG. 9 is a sectional view showing another modified position of one ofthe resonance holes of the silencer according to the fourth embodimentillustrated in FIG. 6;

FIG. 10 is a sectional view showing a modified position of the resonanceholes of the silencer according to the fourth embodiment illustrated inFIG. 6;

FIG. 11 is a sectional view showing a silencer for a vehicle airconditioning system according to a fifth embodiment of the presentinvention; and

FIG. 12 is a sectional view showing a silencer for a vehicle airconditioning system according to a sixth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Certain preferred embodiments of a silencer for a vehicle airconditioning system according to the present invention will now bedescribed in detail with reference to the accompanying drawings.

First Embodiment

Referring first to FIG. 3, a silencer for a vehicle air conditioningsystem according to the present invention includes a silencer body tube10 and an external resonance tube 20 installed on an outercircumferential surface of the silencer body tube 10.

The silencer body tube 10 is arranged between coolant pipes 30 and isequal in inner diameter B to the coolant pipes 30. A coolant gas havinga high temperature and a high pressure, which flows through the coolantpipes 30, is introduced into the silencer body tube 10. Since thesilencer body tube 10 has an inner diameter B equal to the innerdiameter of the coolant pipes 30, the coolant gas flowing through thecoolant pipes 30 passes through the silencer body tube 10 with littleflow resistance. This means that the silencer body tube 10 does notimpair the fluidity of the coolant gas flowing therethrough.

The silencer body tube 10 is installed at an inclination of specificangle θ with respect to a ground surface. For example, the silencer bodytube 10 is installed at an angle of about 90 degrees with respect to theground surface.

In the present embodiment, the silencer body tube 10 is funnedindependently of the coolant pipes 30 and is installed between thecoolant pipes 30. However, if necessary, the coolant pipes 30 may beused as the silencer body tube 10. In this case, it is possible toreduce the manufacturing costs and the number of manufacturing steps.This helps save the costs involved in manufacturing the silencer.

The external resonance tube 20 is fixedly secured to the outercircumferential surface of the silencer body tube 10 having a specificinclination angle θ with respect to the ground surface. The intermediateportion of the external resonance tube 20 is spaced apart from the outercircumferential surface of the silencer body tube 10. The opposite endportions of the external resonance tube 20 are air-tightly fixed to theouter circumferential surface of the silencer body tube 10. Thus, aresonance chamber 22 is defined between the silencer body tube 10 andthe external resonance tube 20.

The external resonance tube 20 includes end fixing portions 20 a havinga diameter smaller than the diameter of the intermediate portionthereof. The end fixing portions 20 a are welded to the outercircumferential surface of the silencer body tube 10 such that theintermediate portion of the external resonance tube 20 is spaced apartfrom the outer circumferential surface of the silencer body tube 10.

In the present embodiment, the silencer body tube 10 has one or moreresonance holes 12 formed in the thickness direction thereof. Theresonance holes 12 are formed to extend from the inside of the silencerbody tube 10 toward the resonance chamber 22 such that a vibration and anoise of a coolant gas flowing through the silencer body tube 10 aretransmitted into and absorbed by the resonance chamber 22.

Accordingly, it is possible to prevent the vibration and the noise ofthe coolant gas from being transmitted into a vehicle room along thecoolant pipes 30. This makes it possible to suppress impairment ofvehicle ride comfort which may be caused by the vibration and the noiseof the coolant gas.

It is desired that the number of the resonance holes 12 is two or more.The resonance holes 12 are formed in the silencer body tube 10 so as tocommunicate with the resonance chamber 22. It is preferred that theresonance holes 12 are formed in a portion of the silencer body tube 10corresponding to a gravity-direction lower region of the resonancechamber 22 having a length C of one half or less of a total length L ofthe resonance chamber 22.

Also desired, the resonance holes 12 are formed in a portion of thesilencer body tube 10 corresponding to a gravity-direction lowermostregion of the resonance chamber 22 having the total length L.

The reason for employing this configuration is to make sure that, evenif compressor-lubricating oil mixed in the coolant gas is introducedinto the resonance chamber 22, the oil is allowed to flow down in thegravity direction and is discharged into the silencer body tube 10through the resonance holes 12.

This makes it possible to prevent the compressor-lubricating oil fromstagnating within the resonance chamber 22. As a result, it is possibleto suppress a reduction in the compressor performance and a reduction inthe vibration/noise absorption rate, which may be caused by thestagnation of the oil in the resonance chamber 22.

Second Embodiment

Next, a silencer for a vehicle air conditioning system according to asecond embodiment of the present invention will be described withreference to FIG. 4.

In the silencer according to the second embodiment, the silencer bodytube 10 is installed at an angle of about 60 degrees with respect to theground surface. As the silencer body tube 10 is installed at an angle ofabout 60 degrees in this way, the external resonance tube 20 existingaround the silencer body tube 10 is also installed at an angle of about60 degrees with respect to the ground surface. Thus, the silencer as awhole is installed at an angle of about 60 degrees with respect to theground surface.

According to the silencer configured as above, just like the silencershown in FIG. 3, it is possible to prevent the compressor-lubricatingoil from stagnating within the resonance chamber 22. As a result, it ispossible to suppress a reduction in the compressor performance and areduction in the vibration/noise absorption rate, which may be caused bythe stagnation of the oil in the resonance chamber 22.

Third Embodiment

Next, a silencer for a vehicle air conditioning system according to athird embodiment of the present invention will be described withreference to FIG. 5.

In the silencer according to the third embodiment, the silencer bodytube 10 has a plurality of resonance holes 12. The resonance holes 12include a resonance hole 12 a formed in a gravity-direction lowerportion of the silencer body tube 10 and a resonance hole 12 b formed ina gravity-direction upper portion of the silencer body tube 10.

In particular, the resonance hole 12 a is formed in a gravity-directionlowermost portion of the silencer body tube 10. The resonance hole 12 bis formed in a gravity-direction uppermost portion of the silencer bodytube 10.

The reason for employing this configuration is to make sure that, evenwhen the silencer body tube 10 is upside down in a process of assemblingthe silencer body tube 10 with the coolant pipes 30, at least one of theresonance holes 12 is always arranged at the gravity-direction lowerside of the resonance chamber 22. This ensures that the oil introducedinto the resonance chamber 22 is smoothly discharged from the resonancechamber 22.

Accordingly, even if the silencer body tube 10 is upside down in anassembling process, it is possible to prevent the compressor-lubricatingoil from stagnating within the resonance chamber 22. As a result, it ispossible to suppress a reduction in the compressor performance and areduction in the vibration/noise absorption rate, which may be caused bythe stagnation of the oil in the resonance chamber 22.

Fourth Embodiment

Next, a silencer for a vehicle air conditioning system according to afourth embodiment of the present invention will be described withreference to FIGS. 6-9.

Referring to FIG. 6, the silencer according to the fourth embodimentincludes a silencer body tube 10 horizontally installed in a parallelrelationship with a ground surface.

As the silencer body tube 10 is horizontally installed in this way, theexternal resonance tube 20 existing around the silencer body tube 10 isalso horizontally installed. Thus, the silencer as a whole ishorizontally installed in a parallel relationship with the groundsurface.

In the silencer according to the fourth embodiment, the silencer bodytube 10 has a plurality of resonance holes 12 formed therethrough. Theresonance holes 12 include a resonance hole 12 c formed in a bottomsurface portion of the silencer body tube 10 corresponding to agravity-direction lowermost region of the resonance chamber 22.

If compressor-lubricating oil mixed in the coolant gas is introducedinto the resonance chamber 22 through the resonance holes 12, the oil isstagnated within the resonance chamber 22 and is accumulated up to alevel of the resonance hole 12 c as shown in FIG. 7. By forming theresonance hole 12 c in the lowermost position in the gravity direction,it is possible to lower the level of the oil stagnating within theresonance chamber 22. This makes it possible to minimize the amount ofthe oil stagnating within the resonance chamber 22. As a result, it ispossible to suppress a reduction in the compressor performance and areduction in the vibration/noise absorption rate, which may be caused bythe stagnation of the oil in the resonance chamber 22.

The plurality of resonance holes 12 further includes a resonance hole 12d preferably formed higher than the resonance hole 12 c formed in thebottom surface portion of the silencer body tube 10. More desirably, theresonance hole 12 d is formed in a top surface portion of the silencerbody tube 10 corresponding to a gravity-direction uppermost region ofthe resonance chamber 22.

There is a fear that the resonance hole 12 c formed in the bottomsurface portion of the silencer body tube 10 is clogged by the oilstagnating within the resonance chamber 22. In this case, the vibrationand the noise generated within the silencer body tube 10 can beintroduced into the resonance chamber 22 through the resonance hole 12 dformed in the top surface portion of the silencer body tube 10 and notinto the clogged resonance hole 12 c formed in the bottom surfaceportion of the silencer body tube 10.

It is most desired that the resonance hole 12 d is formed in the topsurface portion of the silencer body tube 10. In some cases, as shown inFIGS. 8 and 9, the resonance hole 12 d may be formed in the side surfaceportion of the silencer body tube 10.

In FIG. 10, there is shown a modified example of the resonance holes 12formed in the silencer body tube 10. The resonance holes 12 according tothe modified example include a resonance hole 12 c formed in a lowerright portion of the silencer body tube 10 and a resonance hole 12 dformed in an upper left portion of the silencer body tube 10.

In particular, the resonance hole 12 c is formed in a gravity-directionlowermost right portion of the silencer body tube 10. The resonance hole12 d is formed in a gravity-direction uppermost left portion of thesilencer body tube 10.

The reason for employing this configuration is to make sure that, evenif the silencer body tube 10 is 180 degrees turned in the left-rightdirection in a process of assembling the silencer body tube 10 with thecoolant pipes 30, a worker can properly cope with the situation.

Fifth Embodiment

Next, a silencer for a vehicle air conditioning system according to afifth embodiment of the present invention will be described withreference to FIG. 11.

In the silencer according to the fifth embodiment, the silencer bodytube 10 includes a correct position indicating portion 40 formed on anouter circumferential surface thereof. The correct position indicatingportion 40 is designed to indicate a correct position of the externalresonance tube 20 with respect to the resonance holes 12. The correctposition indicating portion 40 is composed of, e.g., a protrusion bead42 protruding radially outward from the outer circumferential surface ofthe silencer body tube 10.

Prior to assembling the external resonance tube 20 with the silencerbody tube 10, the protrusion bead 42 is formed in conformity with acorrect position of the external resonance tube 20 relative to theresonance holes 12. Particularly, the protrusion bead 42 is previouslyformed in one of two axially spaced-apart regions of the silencer bodytube 10 corresponding to the correct position of the external resonancetube 20.

When the external resonance tube 20 is fitted to the outercircumferential surface of the silencer body tube 10, one end portion ofthe external resonance tube 20 is stopped by the protrusion bead 42 ofthe correct position indicating portion 40. This enables a worker torecognize an accurate assembling position of the external resonance tube20 relative to the resonance holes 12. Accordingly, the worker canassemble the external resonance tube 20 in an accurate position withrespect to the resonance holes 12. As a result, the resonance holes 12and the resonance chamber 22 are accurately arranged in a predeterminedpositional relationship with each other. This makes it possible toimprove the noise absorption performance of the resonance chamber 22,thereby significantly enhancing the noise absorption performance of thesilencer.

The protrusion bead 42 of the correct position indicating portion 40 isformed to protrude radially outward by subjecting the silencer body tube10 to a forming process. An end fixing portion 20 a of the externalresonance tube 20 is welded to the protrusion bead 42 thus formed. Thus,the external resonance tube 20 arranged in the correct position isfixedly secured to the outer circumferential surface of the silencerbody tube 10.

A circumferentially-extending welding groove 14 is formed on the outercircumferential surface of the silencer body tube 10 in a positioncorresponding to the end fixing portion 20 a of the external resonancetube 20. The welding groove 14 is formed to protrude radially inward bysubjecting the silencer body tube 10 to a forming process. The weldinggroove 14 is formed on the outer circumferential surface of the silencerbody tube 10 between the end fixing portion 20 a of the externalresonance tube 20 and the protrusion bead 42.

When the end fixing portion 20 a of the external resonance tube 20 iswelded to the protrusion bead 42, a melt welding metal is accommodatedwithin the welding groove 14. Particularly, the welding groove 14enables the melt welding metal to flow into between the end fixingportion 20 a of the external resonance tube 20 and the silencer bodytube 10. Thus, the end fixing portion 20 a of the external resonancetube 20 and the silencer body tube 10 are reliably welded together. Thisenhances the welding reliability of the external resonance tube 20 andthe silencer body tube 10.

According to the silencer of the fifth embodiment, the accurateassembling position of the external resonance tube 20 is marked on thesilencer body tube 10 in advance. The external resonance tube 20 isassembled on the basis of the mark. This makes it possible to easily andrapidly assemble the external resonance tube 20 in a correct position.

Since the external resonance tube 20 can be easily and rapidly assembledin a correct position, it is possible to easily and rapidly perform theassembling work of the external resonance tube 20 and to accuratelyarrange the external resonance tube 20 with respect to the resonanceholes 12. This makes it possible to enhance the productivity and tosignificantly improve the noise absorption performance of the silencer.

Sixth Embodiment

Next, a silencer for a vehicle air conditioning system according to asixth embodiment of the present invention will be described withreference to FIG. 12.

In the silencer according to the sixth embodiment, the silencer bodytube 10 includes two correct position indicating portions 40 formed attwo points on an outer circumferential surface thereof. Particularly,the correct position indicating portions 40 are formed at two pointscorresponding to the correct position of the external resonance tube 20.

The two correct position indicating portions 40 are formed to extendradially outward in two positions on the silencer body tube 10 inconformity with the correct position of the external resonance tube 20.When the external resonance tube 20 is fitted to the outercircumferential surface of the silencer body tube 10, the opposite endportions of the external resonance tube 20 are aligned with the twocorrect position indicating portions 40.

This enables a worker to clearly recognize a correct assembling positionof the external resonance tube 20 with respect to the resonance holes12. Accordingly, the worker can assemble the external resonance tube 20in an accurate position with respect to the resonance holes 12. As aresult, the resonance holes 12 and the resonance chamber 22 areaccurately arranged in a predetermined positional relationship with eachother.

The two correct position indicating portions 40 of the presentembodiment have the same structure as the correct position indicatingportion 40 of the fifth embodiment. The welding structure of thesilencer body tube 10 and the external resonance tube 20 is alsoidentical with the welding structure described above in respect of thefifth embodiment. Thus, the detailed description thereon will beomitted.

In the silencer according to the sixth embodiment, the two correctposition indicating portions 40 protrude radially outward from twoaxially spaced-apart regions of the silencer body tube 10. For thatreason, when assembling the external resonance tube 20, the correctposition indicating portions 40 may hinder the assembling work of theexternal resonance tube 20. However, the correct position indicatingportions 40 are shown on an exaggerated scale in FIG. 12 for the purposeof clarity. In reality, the correct position indicating portions 40 havesuch a size that, during the assembling process, the external resonancetube 20 can be fitted between the correct position indicating portions40 along the outer circumferential surface of the silencer body tube 10as a result of the external resonance tube 20 being elastically deformedradially outward.

While certain preferred embodiments of the invention have been describedabove, the present invention is not limited to these embodiments. It isto be understood that various changes and modifications may be madewithout departing from the scope of the invention defined in the claims.

What is claimed is:
 1. A silencer for reducing noise and vibrationtransmitted through a coolant pipe conveying a coolant gas and alubricating oil therethrough, the silencer comprising: a silencer bodytube including a plurality of resonance holes formed in an outercircumferential surface thereof, wherein the silencer body tube isoriented at a predetermined angle with respect to a ground surface; andan external resonance tube disposed around the outer circumferentialsurface of the silencer body tube, wherein a resonance chamber forabsorbing a vibration and a noise of the coolant gas flowing through thesilencer body tube is defined between the outer circumferential surfaceof the silencer body tube and the external resonance tube, and whereinthe plurality of resonance holes provide fluid communication between thesilencer body tube and the resonance chamber and lubricating oilintroduced into the resonance chamber flows downward in a gravitydirection and is discharged into the silencer body tube through theplurality of resonance holes, wherein each of the plurality of resonanceholes is formed in a portion of the silencer body tube corresponding toa gravity direction lowermost region of the resonance chamber.
 2. Thesilencer of claim 1, wherein the silencer body tube is coaxial with andin fluid communication with the coolant pipe to cause the coolant gasflowing through the coolant pipe to flow through the silencer body tube.3. The silencer of claim 2, wherein the silencer body tube has an innerdiameter that is substantially equal to an inner diameter of the coolantpipe.
 4. The silencer of claim 1, wherein the silencer body tube isformed from a portion of the coolant pipe conveying the coolant gastherethrough.
 5. The silencer of claim 1, wherein the external resonancetube has a first end and a second end each abutting the outercircumferential surface of the silencer tube body, wherein anintermediate portion of the external resonance tube is spaced apart fromthe outer circumferential surface of the silencer body tube to form theresonance chamber.
 6. A silencer for reducing noise and vibrationtransmitted through a coolant pipe conveying a coolant gas and alubricating oil therethrough, the silencer comprising: a silencer bodytube including a plurality of resonance holes formed in an outercircumferential surface thereof, the silencer body tube horizontallyarranged parallel to a ground surface, a first resonance hole of theplurality of resonance holes formed in a lowermost portion of thesilencer body tube in a gravity direction and a second resonance hole ofthe plurality of resonance holes formed in an uppermost portion of thesilencer body tube in a gravity direction, wherein the first resonancehole is formed adjacent a first longitudinal end of the silencer bodytube and the second resonance hole is formed adjacent a secondlongitudinal end of the silencer body tube; and an external resonancetube disposed around the outer circumferential surface of the silencerbody tube, wherein a resonance chamber for absorbing a vibration and anoise of the coolant gas flowing through the silencer body tube isdefined between the outer circumferential surface of the silencer bodytube and the external resonance tube, and wherein the plurality ofresonance holes provide fluid communication between the silencer bodytube and the resonance chamber and lubricating oil introduced into theresonance chamber flows downward in a gravity direction and isdischarged into the silencer body tube through at least one of theplurality of resonance holes.
 7. A silencer for reducing noise andvibration transmitted through a coolant pipe conveying a coolant gas anda lubricating oil therethrough, the silencer comprising: a silencer bodytube including a plurality of resonance holes formed in an outercircumferential surface thereof, wherein the silencer body tube includesa first correct position indicating portion formed therein to indicate acorrect placement of a first end of the external resonance tube relativeto the silencer body tube, wherein the first correct position indicatingportion includes a protrusion bead protruding outwardly from the outercircumferential surface of the silencer body tube; and an externalresonance tube disposed around the outer circumferential surface of thesilencer body tube, wherein a resonance chamber for absorbing avibration and a noise of the coolant gas flowing through the silencerbody tube is defined between the outer circumferential surface of thesilencer body tube and the external resonance tube, and wherein theplurality of resonance holes provides fluid communication between thesilencer body tube and the resonance chamber and lubricating oilintroduced into the resonance chamber flows downward in a gravitydirection and is discharged into the silencer body tube through at leastone of the plurality of resonance holes, wherein the protrusion beadprotrudes from a portion of the outer circumferential surface of thesilencer body tube corresponding to a position of one end of theexternal resonance tube.
 8. The silencer of claim 7, wherein thesilencer body tube includes a second correct position indicating portionformed in the silencer body tube axially spaced apart from the firstcorrect position indicating portion, wherein the second correct positionindicating portion corresponds to a position of a second end of theexternal resonance tube.
 9. The silencer of claim 7, wherein theprotrusion bead protrudes radially outwardly from the outercircumferential surface of the silencer body tube and is formed bysubjecting the silencer body tube to a forming process, and wherein theexternal resonance tube is welded to the protrusion bead.
 10. Thesilencer of claim 9, wherein the silencer body tube further comprises awelding groove formed on the outer circumferential surface of thesilencer body tube, wherein the welding groove is configured to receivea melted welding metal when the external resonance tube is welded to theprotrusion bead.
 11. A silencer for reducing noise and vibrationtransmitted through a coolant pipe conveying a coolant gas and alubricating oil therethrough, the silencer comprising: a silencer bodytube including at least one resonance hole formed in an outercircumferential surface thereof, wherein the silencer body is disposedcoaxially with and in fluid communication with the coolant pipe to causethe coolant gas flowing through the coolant pipe to flow through thesilencer body tube and the silencer body tube has an inner diametersubstantially equal to the inner diameter of the coolant pipe; and anexternal resonance tube disposed around the outer circumferentialsurface of the silencer body tube, wherein a resonance chamber forabsorbing a vibration and a noise of the coolant gas flowing through thesilencer body tube is defined between the outer circumferential surfaceof the silencer body tube and the external resonance tube and each ofthe at least one resonance holes provides fluid communication betweenthe silencer body tube and the resonance chamber, wherein one of theresonance holes is formed in a gravity direction lowermost portion ofthe silencer body tube surrounded by the resonance chamber andlubricating oil introduced into the resonance chamber flows downward ina gravity direction and is discharged into the silencer body tubethrough the one resonance hole.